1. Field Of The Invention
This invention relates to a pneumatic tool, more particularly to a pneumatic tool which is easy to operate and which can be manufactured and assembled conveniently.
2. Description Of The Related Art
Referring to FIG. 1, a conventional pneumatic wrench is shown to comprise a main body (1) which has a hollow body part (11) with an open front end and an open rear end (111). A pneumatic driving unit (12) is received in the body part (11) and has a driving shaft that extends out of the body part (11) via the front end of the latter. The open rear end (111) of the body part (11) has a cover member (13) mounted securely thereon. The cover member (13) is formed with a first air intake guiding slot (131) and a second air intake guiding slot (132), both of which are communicated with the body part (11) so as to guide air flow into the interior of the body part (11). The main body (1) further includes a handle part that extends downwardly from the body part (11). The handle part has a horizontal positioning passage (14) provided at the junction of the body part (11) and the handle part, an air intake passage (15) that extends downwardly from the positioning passage (14), a sliding passage (16) that intersects with the air intake passage (15), a recess (17) that is formed in a front surface of the handle part and that is communicated with the sliding passage (16), and an air intake mouth (18) provided in a bottom surface of the handle part and communicated with the air intake passage (15). An air flow direction control unit (21) includes a hollow tubular member (211) which is positioned in the positioning passage (14). The hollow tubular member (211) has a radial hole (212) which is communicated with the air intake passage (15). The hollow tubular member (211) further has a first vent (216) and a second vent (217) formed radially on the periphery thereof at two sides of the radial hole (212). A control rod (213) is disposed movably in the tubular member (211) and has a first diameter-reduced portion (214) formed at one end portion thereof and a second diameter-reduced portion (215) formed at the other end portion thereof. The control rod (213) is movable between a first position, wherein the first diameter-reduced portion (214) is communicated with the first vent (216) and the second vent (217) is blocked, and a second position, wherein the second diameter-reduced portion (215) is communicated with the second vent (217) and the first vent (216) is blocked. The first vent (216) is communicated with the first guiding slot (131) in the cover member (13) via a first connecting passage (not shown) which is formed in the body part (11) of the main body (1). Similarly, the second vent (217) is communicated with the second guiding slot (132) in the cover member (13) via a second connecting passage (141) which is formed in the body part (11) of the main body (1). An air flow regulating assembly (22) includes an air flow regulating ring (222) disposed axially and fittingly inside the air intake passage (15) and formed with a plurality of differently-sized angularly spaced radial holes (223). A rotary knob (221) is mounted rotatably on the bottom surface of the handle part and is connected securely to the regulating ring (222) so that the rotary knob (221) is operable to align one of the radial holes (223) in the regulating ring (222) with the air intake mouth (18). A trigger assembly (23) includes a trigger rod (231) which is disposed movably and fittingly in the sliding passage (16), a trigger piece (232) which is mounted movably on the front surface of the handle part and which is connected securely to one end of the trigger rod (231), and a coupling head (233) which is mounted securely on the bottom surface of the handle part to communicate the air intake mouth (18) with an air source (not shown). The coupling head (233) has a spring unit (234) disposed therein, a steel ball unit (235) disposed in the coupling head (233) and biased by the spring unit (234) to block the coupling head (233), and a washer (236) to position the steel ball unit (235) in the coupling head (233).
When the driving unit (12) is operated to rotate in a counterclockwise direction and the amount of air intake is maximum, the control rod (213) is in the second position, and the radial hole (223) with the greatest diameter in the regulating ring (222) is communicated with the air intake mouth (18). The steel ball unit (235) is pushed by the trigger rod (231) to compress the spring unit (234) of the coupling head (233) when the trigger piece (232) is pressed to move the trigger rod (231) so as to permit air flow from the air source through the coupling head (233) into the air intake mouth (18) via the gap formed between the washer (236) and the steel ball unit (235). Air then flows into the air intake passage (15) via the regulating ring (222), through the connecting passage (141) in the body part (11) via the radial hole (212) in the tubular member (211) and the second diameter-reduced portion (215) of the control rod (213), and into the interior of the body part (11) via the second guiding slot (132) in the cover member (13) so as to activate the driving unit (12) to rotate the driving shaft in the counterclockwise direction. When the driving shaft of the driving unit (12) is to be rotated in a clockwise direction, the control rod (213) is moved to the first position. At this stage, air flows into the body part (11) via the first guiding slot (131) in the cover member (13) when the trigger piece (232) is pressed, thus activating the driving unit (12) to drive the driving shaft to rotate in the clockwise direction.
To vary the amount of air intake, the rotary knob (221) is operated to rotate the regulating ring (222) so as to align the air take mouth (18) with a differently-sized radial hole (223') in the regulating ring (222). When the trigger piece (232) is released, the spring unit (234) biases the steel ball unit (235) to block the coupling head (233) so as to stop air flow through the air intake mouth (18). The main body (1) further includes an air outlet (not shown) so as to permit the flow of air from the body part (11). Since the structure of the air outlet is not related directly to the present invention, a description thereof will be omitted for brevity.
Although, the above-described conventional pneumatic tool is effective, the assembly of the same is relatively complicated. To assemble the air flow direction control unit (21), the air flow regulating assembly (22) and the trigger assembly (23) in the main body (1), a plurality of air passages must be formed in the main body (1). Since the air passages are communicated with each other, and since the relative position of the air passages is complicated, precise machining of the main body (1) must be processed.
Therefore, the main drawback of the above-described convention pneumatic tool is that the manufacture and assembly thereof is time-consuming and relatively complicated.